Electro-optic current sensor with high dynamic range and accuracy

ABSTRACT

An optical sensor assembly that senses current in a secondary electrical cable while sensing voltage in a primary electrical cable. The optical sensor assembly may include a sensor body, a concentrator core for measuring current. The concentrator core may be attached to a first end of the sensor body. The optical sensor assembly may include a plurality of extension arms that extend from the sensor body. The extension arms may include clamping devices on one end that are configured to attach to a first electrical cable. The concentrator core may be configured to at least partially surround a second electrical cable and sense the current from that second electrical cable.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/389,752, filed on Dec. 23, 2016, which is a divisionalapplication of U.S. Pat. No. 9,535,097 filed May 15, 2014, which claimsthe benefit of U.S. Provisional Patent Application Ser. No. 61/823,849,filed May 15, 2013, entitled, “Electro-Optic Current Sensor With HighDynamic Range and Accuracy,” and is a continuation-in-part of U.S. Pat.No. 9,134,344, filed Jul. 19, 2012, entitled “Optical Sensor AssemblyFor Installation on a Current Carrying Cable,” both of which are herebyincorporated by reference herein in their entireties.

FIELD OF THE PRESENT DISCLOSURE

Aspects of the present disclosure relate to optical sensors, and moreparticularly, to optical sensors used to sense an electrical current ina current carrying cable.

BACKGROUND

A variety of sensors have been developed for measuring current in acurrent carrying cable, such as current in a high voltage electricaldistribution system. Optical current sensors 30 based on thebirefringence of various materials, and the Faraday effect, from themagnetic field, and optical voltage sensors based on the Pockels effect,from the voltage field, are known in the art. Optical current sensors,that use fiber optic cable that surround the current carrying cable,although they may have a suitable dynamic range, require opening thecurrent carrying cable at installation. Hence they are expensive andcumbersome to install.

Optical current sensors utilizing a magnetic concentrator with bulkoptical sensors, (as opposed to fiber optics), in an airgap are alsoknown in the art. One such embodiment is discussed in an article titled“Use of Dual Frequency Excitation Method to Improve the Accuracy of anOptical Current Sensor,” by Shuping Wang, et al, SPIE meeting, August,2009.

Airgaps within powder core magnetic material stabilize the temperaturesensitivity of the magnetic material. Such stabilization, with respectto laminated magnetic core structures, is discussed in the publication“Gapped Magnetic Core Structures,” by Guenter B. Finke, Magnetic MetalsCorporation, Camden, N.J. 08101.

Blake, U.S. Pat. No. 6,166,816, describes the use of one light sourcefor a combined fiber optic current and voltage sensor. It is, however,difficult to make use of the current sensor disclosed. The electricutility company can use it during a new set up or take apart the currentcarrying cable for installation.

Ishiko et al., U.S. Pat. No. 4,999,571, describes a clamp-on opticalcurrent and voltage sensor. The sensor must be attached to the line whenthe voltage to the line is off. The crystal used in the current sensoris a garnet crystal, which is temperature sensitive. The sensor alsouses a quarter-wave plate in connection with the voltage sensor and suchquarter-wave plate is also temperature sensitive. In Ishiko, the currentcarrying cable is not firmly held by the device until the U-shaped,magnetic core is in its closed position.

Bjorn, U.S. Pat. No. 7,068,025, teaches a simplified sensor, a smallglass rod lying on the current carrying cable. Based on the Faradayeffect, rotation of the plane of polarization of polarized light in theglass rod is proportional to the intensity of the magnetic fieldsurrounding the cable. The strength of the magnetic field surroundingthe conductor is in accordance with the level of electric currentpassing through the conductor. The Bjorn patent teaches a method inwhich the sensor samples only one locality and only for a short distancealong the conductor.

C.V. Temple et al., U.S. Pat. No. 2,709,800, teaches a power line faultdetector that allows mechanical adjustment of the airgap of aconcentrator and inductive coupling for detecting various levels ofcurrent. This sensor may only be used for the detection of faultcurrents.

Bosselmann et al., U.S. Pat. No. 5,963,026, discloses two Faradayelements or crystals for two 5 different measurement ranges of currentin order to achieve a higher dynamic range. This adds to the complexityand the cost.

The prior art teaches various devices and methods for measuring thecurrent in real time in a current carrying cable using optical sensors.However, the prior art does not teach an economical, simple sensorassembly design for accurate measurements across a large dynamic range,sensitivity and bandwidth, that is capable of being installed on thecable without disturbing the operating function of the cable. Thepresent disclosure fulfills these and other needs and provides furtherrelated advantages as described in the following summary.

A need also exists for a small, compact current sensor that is highlysensitive to a magnetic field of interest but highly insensitive tounwanted magnetic fields, such as from nearby current carrying cables.

BRIEF SUMMARY

An aspect of the present disclosure relates to an optical sensorassembly for installation on an electrical current carrying cable andsensing much information about the current in the cable, and, further,embodiments of an optical sensor assembly combined with an electronicssystems, (preferably, located a distance away from the cable), andcapable of one or more of sensing, measuring, indicating, analyzing andevaluating the current in the cable.

According to an aspect, the present disclosure provides an opticalsensor assembly for sensing current in a current carrying cable by amagnetic concentrator creating a magnetic field, from said cable,representing current in the cable, and optical sensing of the magneticfield of the cable to provide electrical signals representing the sensedcurrent. By combining such optical sensor assembly with an electronicssystem having a computing device, data processing system or the like,such electrical signals may then be analyzed and evaluated to provide awide range of information concerning an electrical power distributionsystem.

It is understood that the “current” in a power distribution cable, (andeven in other current carrying wires or cables), may well be comprisedof a plurality of components having a myriad of amplitudes andfrequencies, as well as direct currents, (DC). As used herein, “current”is intended to comprehend a “single current” (that is, a current ofsingular amplitude and singular frequency and, also, DC current), and,as well, “a current having a plurality of component current frequenciesor amplitudes, or both, as well as, DC.”

An objective is to provide an optical sensor assembly for installationon a current carrying cable without having to disrupt the function ofthe cable.

Still another objective, in an aspect of this disclosure, is to providean optical sensor assembly in combination with an electronics system,having a wide dynamic range and sensitivity of measurement that canperform one or more of many features, such as, but not limited to,identification, measurement, display and indication, analysis,evaluation and reporting of information, indicative of thecharacteristics of current flowing in a cable.

A further aspect of the present disclosure relates to an electro-opticcurrent sensor with a polarizing beam splitter having a low Verdetconstant. The sensor material has a high Verdet constant and ispositioned very close to the polarizing beam splitter. The materialcomposition and spatial arrangement of the PBS relative to the sensormaterial operate to reduce effects of extraneous electromagneticinterference from adjacent conductors that produce interferingelectromagnetic fields. Instead of a polarizing beam splitter, azero-order waveplate can be used to polarize the light along a lineardirection, allowing the overall size of the current sensor to be reducedto a very compact size.

Another aspect of the present disclosure relates to a device and methodfor installing voltage/current sensor assemblies onto a primaryelectrical cable, while permitting the voltage/current sensor to monitorcurrent of a secondary electrical cable that taps off of the primarycable. The sensor assembly allows voltage to be monitored on the primaryelectrical cable while enabling measurement of current on secondary orauxiliary cables that feed circuits off of the primary cable. Theability to monitor current through a secondary electrical cable whilesimultaneously monitoring voltage from a primary electrical cable can beused on with electrical distribution grid, such that the optical sensorenables real-time feedback on power usage, allowing distributionutilities to closely monitor and control electricity distribution.

Other features and advantages of the present disclosure will becomeapparent from the following more detailed description, taken inconjunction with the accompanying drawings, which illustrate, by way ofexample, the principles of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an optical sensor assembly when amagnetic concentrator is in open position, according to one embodimentof the present disclosure.

FIG. 2 is a perspective front view of FIG. 1 showing the magneticconcentrator is in a closed position.

FIG. 3 is a side elevation view of FIG. 1 showing the magneticconcentrator in the open position.

FIG. 4 is a side elevation view of FIG. 2, showing the magneticconcentrator in the closed position.

FIG. 5A is a side elevation, cross-section view of a powder coremagnetic concentrator, closed, as in FIGS. 2 and 4, in relation to thecable and the current sensor. The magnetic concentrator furtherillustrates the airgap in the magnetic concentrator, according to oneembodiment of the disclosure.

FIG. 5B is a side elevation, illustrating an alternative magnetic coreconstruction, in cross-section, and an alternative location of theairgap and an optical current sensor within the airgap. Also shown arethe input to and outputs from the optical current sensor.

FIG. 6 is a side elevation, cross-section view of a hinged, laminatedmagnetic concentrator illustrating an airgap in the magneticconcentrator and having laminations of strips of magnetic materialadhered together adhesively and/or in a medium of non-magnetic 30material, in some embodiments of the disclosure.

FIG. 7A is a side elevation view of a revised version of the opticalsensor assembly, using an alternative mechanical structure of clamp andhousing, using, for example, the alternative embodiment of magnetic coreand sensor shown in FIG. 5B. The housing of the magnetic concentrator isshown in closed position and the exterior of the optical sensor assemblyis shown.

FIG. 7B is a front elevation view of the optical sensor assembly showingthe optical fiber cables attached at the bottom thereof.

FIG. 7C is a front view of the optical sensor assembly, illustrating itsexterior, with the magnetic concentrator open and showing the cableclamps holding a current carrying cable and the optical fibers extendingfrom the bottom of the optical sensor assembly.

FIG. 7D is a side elevation view of the optical sensor assembly inpartial cross-section, illustrating its interior.

FIG. 8A is an illustration of the optical sensor assembly according toone embodiment of the disclosure, wherein the assembly is suspended froma current carrying cable of a high voltage electrical distributionsystem and connected to an electronics system for analysis and/or otherevaluation of the current in the cable and thence connected, at itsoutput, to further components or systems;

FIG. 8B is an illustration of a second embodiment thereof in which theoutput is connected to possible alternative components or systems;

FIG. 8C is an illustration of a third embodiment thereof;

FIG. 8D is an illustration of a fourth embodiment thereof illustratingoutputs to wireless and wired communications systems;

FIG. 9 is a schematic diagram of one embodiment of the electronicssystems of FIGS. 8A-8D, which electronics systems, among othercapabilities, process, analyze and evaluate the information as to thecurrent in the cable and provides outputs therefrom. FIG. 9, includes adevice such as a computing device, a digital signal processor or amicroprocessor or the like;

FIG. 10 is an illustration of an optical current sensor comprising alight source and polarizer providing polarized light which istransmitted through a light directing device and out into a polarizingbeamsplitter and thence to the light sensors of a light analyzer;

FIG. 11 is an illustration of a light directing device in which thepolarized light passes twice through the light directing device andprovides an output doubly affected by the Faraday effect;

FIG. 12 is another illustration of an optical current sensor, showing alight source, a polarizer and, thus, polarized light passing through thereflective prism, to be affected by the Faraday effect of a magneticfield H. The light, passing out of the reflective prism to a polarizingbeamsplitter is then turned into electrical signals by the lightdetectors.

FIG. 13 is an embodiment of a light directing device in linear form,receiving light through an input polarizer and reflecting it through thelight directing device wherein it is rotated by exposure to a magneticfield H. The light then travels to an output through a polarizingbeamsplitter for further transmission of the light through opticalfibers to light detectors.

FIG. 14 is an embodiment in which the input light is in line with thelight directing device. The input polarizer reflects the beam of lightinto the light directing device, wherein it is exposed to a magneticfield H and then reflected out from the light directing device by apolarizing beamsplitter.

FIG. 15 is an embodiment in which the input light enters the lightdirecting device without reflection and is reflected out of the lightdirecting device by an output polarizing beamsplitter.

FIG. 16 is a functional block diagram of an optical sensor composed ofmaterials having disparate Verdet constants.

FIG. 17 is a cutaway view of an optical sensor assembly oriented suchthat the optical fibers extend downward along a y-direction.

FIG. 18 is a perspective view of an optical sensor assembly orientedsuch that the optical fibers extend along a direction parallel to acurrent carrying cable.

FIG. 19 is a perspective illustration of an optical sensor assemblyhaving an output polarizing beamsplitter mounted at a 45 degree anglewith respect a length of a prism from an end edge thereof

FIG. 20 is a perspective illustration of the optical sensor assemblyshown in FIG. 19 with some of the surfaces hidden to reveal someinternal structures and light paths inside the optical sensor.

FIGS. 21A-21D illustrate top, side, and end views of an optical sensorassembly based on the one shown in FIGS. 19 and 20.

FIG. 22 is a perspective illustration of an optical sensor assemblyhaving an output polarizing beamsplitter mounted to a half-wave platethat is mounted to the bottom of a prism.

FIGS. 23A-23C illustrates perspective, side, and end views,respectively, of an optical sensor assembly having a prism mirrormounted to the light output surface of the output polarizingbeamsplitter to direct the output light in a direction along the y-axiswhen the optical sensor assembly is inserted into the airgap as shown inFIG. 18.

FIG. 24 is a perspective illustration of the optical sensor assemblyshown in FIGS. 23A-23C installed into a mechanical structure that isclamped around a current carrying cable.

FIG. 25 is a perspective illustration of an optical sensor assemblyconfigured to connect to primary and secondary electrical cables.

FIG. 26 is an exploded perspective view of the sensor assembly shown inFIG. 25.

FIG. 27 is an exploded perspective view of the sensor assembly as shownin FIGS. 25-26.

FIG. 28 is a top view of the sensor assembly depicted in FIGS. 25-27.

FIG. 29 is a bottom view of the sensor assembly depicted in FIGS. 25-28.

DETAILED DESCRIPTION

FIG. 1 is a perspective view of one embodiment of the optical sensorassembly 10 wherein the magnetic concentrator 54 is in the open positionand has not yet been placed in a position to encompass or partiallyencompass the current carrying cable. It is noted, nevertheless, that inthis position, the current carrying cable 12 is firmly held by theoptical sensor assembly 10.

FIG. 2 is a perspective front view of FIG. 1, showing the magneticconcentrator in closed position showing housing 30 locked in place bylocking element 38.

Referring to FIGS. 1 and 2, the base unit 20, which extends from hooks26 to the bottom of the optical sensor assembly 10, uses two hooks 26,as shown, for hanging the base unit 20 from the current carrying cable12. Only one hook, by itself, or, possibly, with additional ties,strapping or other structure may be used. In the embodiment of FIG. 1, apair of hooks 26, one on either side of a light directing device 44,(which in one embodiment, is shown in FIG. 5B, as being a reflectiveprism 44, of the optical current sensor 40), as discussed in greaterdetail below. Each of the hooks 26 may include a curved portion 28adapted to firmly hold the base unit 20 to the current carrying cable12.

As illustrated in FIGS. 1-4, each hook 26 may further include a clamp29, such as a screw clamp as illustrated, although other clamps andequivalent fasteners may be used. The words “clamp” and “clamps” areintended to include such alternative constructions which will firmlyhold the current carrying cable in fixed position relative to base unit20 at least when the housing is closed. The illustrated clamp 29, forcesthe current carrying cable 12 against the curved portion 28 of the hook26 to secure the base unit 20 to the current carrying cable 12, so thatthe assembly remains physically stable relative to the cable even inrough weather conditions.

In attaching the optical sensor assembly 10 to a current carrying cable12, what is needed is “means for holding the cable firmly,” whether themagnetic concentrator 54 is open or closed. It is to be understood thatthe cable 12 may be held in a fixed position relative to the body of theoptical sensor assembly 10, as shown, or, alternatively, with the clamps29 held in a fixed position with respect to the movable magneticconcentrator 54. In closed, operating position, the magneticconcentrator 54 must encircle the cable 12 or a sufficient amountthereof so as to pick up the magnetic field of cable 12 and extend themagnetic field to the magnetic concentrator's airgap 60 in which theoptical current sensor 40 is disposed when in operating position. Referto FIGS. 5A and 5B for illustration of airgap 60 and optical currentsensor 40. Further, the magnetic field provided by the magneticconcentrator 54 must be strong enough to exclude stray, undesiredmagnetic fields, or else, suitable means against them must be provided.

Among the alternatives to hooks, clamps, fasteners and the like, forholding the current-carrying cable, it is to be appreciated that plasticties, wires, ropes, chains, and all sorts of means may be devised forfirmly holding the current-carrying cable with respect to the opticalsensor assembly. “Clamps” is intended to cover all sorts of hooks,fasteners, jaws, wedges, vices and other devices adapted or adaptable tothe firmly holding of the cable 12.

A concentrator housing 30 is pivotally attached at the top of theoptical sensor assembly 10 and partially encloses the magneticconcentrator 54 and, when in operation, holds it around the currentcarrying cable 12. The concentrator housing 30 has a first end 32 and asecond end 34, illustrated in FIGS. 3 and 4. By also referring to FIGS.3 and 4, it can be seen that a pivot 36 of the second end 34 of theconcentrator housing 30 pivotally attaches the concentrator housing 30such that the concentrator housing 30 moves both itself and the magneticconcentrator 54 between an open position and a closed position. Otherconstructions may be readily designed to properly position the magneticconcentrator 54 around the current carrying cable 12, at least duringoperation of the optical sensor assembly 10.

The structure holding the cable 12, magnetic concentrator 54, and otherelements of the optical sensor assembly 10, is rigidly designed tominimize vibrations that cause erratic readings in the system. It is tobe appreciated that, in operation, the cable 12 is fixedly held, eitherwith respect to the body of the optical sensor assembly 10, or fixedwith respect to the magnetic concentrator 54, whether the magneticconcentrator 54 is open or closed. The preferred embodiment is whereinthe cable 12 is fixedly held with respect to the body of the opticalsensor assembly 10, rather than to the magnetic concentrator 54.

FIGS. 3 and 4 are side elevations of the optical sensor assembly 10.

Referring to FIGS. 3 and 4, it may be seen that in the open position,FIG. 3, the concentrator housing 30 is moved away from the base unit 20.In FIG. 4, the closed position, the concentrator housing 30 positionsthe magnetic concentrator 54 around the current carrying cable 12 suchthat the current carrying cable 12 passes through the airgap 60 to theinterior of the magnetic concentrator 54 without physically touching themagnetic concentrator 54 or the concentrator housing 30.

It is to be understood that other constructions may be devised whereinthe cable 12 need not pass through the airgap 60.

A locking element 38 is provided for removably securing the first end 32of the concentrator housing 30 to the base unit 20 in the closedposition. In the present embodiment, the locking element 38 is ascrew-type clamp attached to the concentrator housing 30 that removablyengages a flange 39 of the base unit 20. The locking element 38 locksthe concentrator housing 30 in the closed position, thereby maintainingthe magnetic concentrator 54 in its position which creates a magneticfield around optical current sensor 40 (not shown) which lies within, orin some embodiments, partially within, the airgap of magneticconcentrator 54.

The portion of base unit 20, from flange 39 downward, is encased in ahigh dielectric insulator, having outer flanges, such as flange 23,which substantially increase the external electric arcing path on theouter surface of the base unit 20. Those skilled in the art know whatmaterial or combinations of materials could be used, such as, but notlimited to, a high dielectric elastomer, rubber, silicon rubber orvarious other materials. Such outer coverings, or sleeves, arecommercially available and may be stretched, form-fitted, previouslymolded or cold or heated, shrink-fitted to the body of the insulateddevice. Other suitable outer surface layers may be utilized having highdielectric insulation, suitable by having high voltage breakdown,weathering and temperature withstanding characteristics.

FIG. 5A is a side elevation, cross-section view of the magneticconcentrator 54, in relation to the current carrying cable 12 and theoptical current sensor 40. As illustrated in FIG. 5A, the opticalcurrent sensor 40 comprises a polarized light input 42, a lightdirecting device, which in this embodiment is a reflective prism 44, anda light output 46. The polarized light input 42 is operably connected toreceive and polarize the light beam from a light source 48, which may beby way of example, but not limited to, a LED or a laser, and the lightoutput 46 is operably connected to provide a light output to a lightanalyzer 50. Polarized light is directed into the reflective prism 44 asa polarized light beam 52. In the reflective prism 44, the portion ofthe polarized light beam 52, parallel to the magnetic field, (thehorizontal portion in the Fig.) is rotated in its polarization by beingexposed to the magnetic field. The rotated, polarized beam of light isreflected out the light output 46, and to the light analyzer 50 whichsenses this rotation, which represents the current level, (and manyother characteristics of the current), and the current direction in thecable.

Light detectors, (not shown, but shown in FIG. 9), as part of the lightanalyzer, but in this embodiment located remotely in the electricalsystem 104, FIG. 9, convert the light signals into electrical signals sothat they can be analyzed and evaluated by an electronics system.

In the discussion herein, the words “optical,” “optics,”“electro-optical” and the like are used for brevity and clarity.However, it is intended that those words, as used herein, are intendedto cover frequencies of electromagnetic radiation not only inside thevisible spectrum, but also frequencies outside the visible spectrum.Such meanings are commonly accepted. See Wikipedia.org, also Webster'sII, New Riverside University Dictionary, 1984 Ed. Also, it is commonlyunderstood by those skilled in the electro-optical art that “light” and“polarized light” include both frequencies inside and outside of thevisible spectrum. Examples of “light” outside the visible spectrum whichoffer possibilities of use, are infrared and ultraviolet frequencies. Ofcourse, the selected frequency or frequencies are those, preferably, forconvenience, economics and reliability for which there are suitableelectrical components available as to sources, conductors, transmitters,detectors, and so forth. Near infrared frequencies, say, for example,but not with limitation, 800 nm to 900 nm are well-suited for meetingthe requirements for application to the optical sensor assembly 10described herein and also for which there are suitable electricalcomponents readily available Infrared frequencies, particularly, thenear infrared, are those commonly used in similar optical devices andare suited for use herein.

As illustrated in FIG. 5A, the magnetic concentrator 54, has a first end56 and a second end 58 that together define an airgap 60 therebetween.The magnetic concentrator 54 is mounted, within a housing 30 that ispivoted, (not shown), so that it fits around the current carrying cable12 when the base unit 20 is hung from the current carrying cable 12 bythe at least one hook 26. When the concentrator housing 30 is moved tothe closed position, the reflective prism 44 is operably positioned inthe airgap 60 of the magnetic concentrator 54.

The distance “D” between the magnetic concentrator 54 and the currentcarrying cable 12 is adjusted so that magnetic concentrator 54 createsan optimum magnetic output, or, at least, a “suitable” output.

The optical current sensor 40, in operation, is positioned in airgap 60to sense the current in the cable 12. Optical current sensor 40 has aclearance within the airgap 60, which helps to reduce sensitivity totemperature. It has been determined that the width of the airgap 60depends on the length of the magnetic concentrator 54. The longer themagnetic concentrator, the greater the airgap may be. In the embodimentshown, a magnetic concentrator of 7 or 8 inches in length would allowusing an airgap of about ¾ of an inch or an inch. Clearance of thereflective prism 44 of the optical current sensor 40, within said airgap60, constructed as shown in FIG. 5A, is about 1/10 of an inch. Suchairgap construction considerably reduces the sensitivity of the systemto temperature. In general, the wider the airgap and the clearance ofsensor 40, the less sensitivity of the system to temperature.

A wider airgap 60 provides a wider and more accurate dynamic range ofcurrent sensing by the reflective prism 44. A light directing device,such as reflective prism 44, in the preferred embodiment herein, that iswider (that is, longer within the airgap and, thus, providing a longerlight path exposed to the Faraday effect), provides a better outputlight signal with a higher signal-to-noise ratio.

The path of the beam within the light directing device, prism 44 in oneembodiment, is preferably closely aligned with the lines of force of themagnetic field. If this is done, a more precise, rotated output and,consequently, more precise electrical signals can be generatedtherefrom. Depending on current sensor 40, and, particularly the lightdirecting device, such as prism 44, other angular alignments may befound suitable.

The light directing device, which, in FIG. 5A is a reflective prism 44,but, it may be any shape, prism or otherwise, that directs the lightfrom the polarized light input 42 to the light output 46. In the presentembodiment, the reflective prism 44 is a prism having a pair of slopedreflective surfaces 62 for directing the beam as described above. Glassprovides benefits such as low temperature sensitivity. Other materialsand shapes of reflective prism 44, its reflective surfaces and fiberoptics configuration may alternatively be used. Some of suchpossibilities are illustrated hereafter in FIGS. 10 through 15.

The light directing device may be a material selected from the group ofnear optical grade glass, or better, bulk glass, diamagnetic glasses,crystals, including, particularly, ferromagnetic crystals, polymers,doped polymers and other materials, having polarized light directingproperties and susceptible to the Faraday effect upon such polarizedlight, and having minimal temperature sensitivity or having atemperature sensitivity that can be suitably corrected or compensatedfor.

Many optical grades of glass or near optical grade and other bulk glassitems are well-suited for a light directing device, including for areflective prism. Some of the most sensitive materials of this kind arediamagnetic glasses and magnetic crystals, determined by a study in theDepartment of Electrical Engineering, Maryland University, College Park,Md., published in Magnetics, IEEE Transactions on May, 1997, Vol. 33,Issue 3 and updated on Aug. 6, 2002.

Other glasses, crystals, polymers, doped polymers and various othermaterials, mixtures and compounds may be found suitable, provided theyconduct polarized light, are susceptible to the Faraday effect for asuitable range of current causing a rotation of the polarized light, andhave minimal temperature sensitivity, or a temperature sensitivity thatcan be corrected, compensated for, calibrated for or otherwise accountedfor. They should also have a suitable frequency response to provideinformation suitable for analysis and evaluation of one or more ofspectral content, harmonics, stray frequencies, and other factors indetermining quality.

Glass, crystal or other materials may well be found suitable for thelight directing device herein, if they are transmissive of polarizedlight beams, magneto-optically sensitive to the Faraday effect, capableof sensing a wide bandwidth of magnetic frequencies, have a wide rangeof response to magnetic fields and have no deficiencies, includingtemperature sensitivity or other deficiency, that cannot be correctedfor, by monitoring, or by “look-up” tables or mathematical formulas in acomputing device or by other means.

From any such light directing device the optical sensor assembly 10combined with an electronics system, as described hereafter inconnection with FIG. 9, can provide the capability for determiningcurrent quality, which is hereby defined as including one or more ofidentification, measurement, display and indication, analysis,evaluation and reporting of one or more of current levels, spectralcontent, harmonics, transients, impedance, faults, fault locations,surges, spikes and power factor and any other characteristics of valueor of interest.

Of course, determination of impedance would require some knowledge as tovoltage in the system and determination of power factor could bedetermined by having voltage zero cross-over information.

The beam of polarized light 52, at some intermediate length withinreflective prism 44, is, preferably, closely aligned parallel with themagnetic field in the airgap 60. The magnetic field in the airgap 60rotates the plane of polarization of the polarized light 52 within thereflective prism 44. This is also sometimes referred to as a “shift”between polarized light components. The amount of rotation isproportional to the strength of the magnetic field in the airgap 60 andthe amount of rotation is measurable by a light analyzer, such as thelight analyzer 50, in order to determine the current in the currentcarrying cable 12. This is more fully illustrated hereafter inconnection with FIG. 10.

In the embodiment of FIG. 5A, the magnetic concentrator 54 is D-shapedand includes a flattened portion 57, with the airgap 60 being positionedin an offset position at the edge of the flattened portion 57, so thatthe cable 12 in the embodiment shown passes through the airgap 60 duringinstallation. In this embodiment, the magnetic concentrator 54 does notinclude any form of break or hinge within its body.

In the embodiment of FIG. 5A, the magnetic concentrator 54 comprises apowder core comprised of magnetic powder mixed with at least one type ofnon-magnetic material and having miniature distributed airgapsthroughout the magnetic concentrator 54. This construction of powdercores is well-known and numerous powder magnetic cores are available.

A powder magnetic core having high saturation level and a narrowhysteresis loop, (to reduce the power loss), are utilized herein.

FIG. 5B, showing the magnetic core and cable in cross-section,illustrates another configuration of the magnetic concentrator 54 ofFIG. 5A, showing magnetic concentrator 54A and an alternative locationof the optical current sensor 40 within the airgap 60 formed between twomagnetic concentrator segments 54B and 54C of the magnetic concentrator54A. Current carrying cable 12 is shown within the central portion ofmagnetic concentrator 54A. The magnetic field of the magneticconcentrator 54A is carried through aluminum panel 79, (which liesbetween the upper part of the core 54 a and the lower magnetic segments54B and 54C, and is part of a larger structure enclosing items lyingbelow magnetic concentrator 54A). The magnetic field extends through thealuminum panel 79 into magnetic segments 54B and 54C, which create amagnetic field in the airgap 60 which lies between them. The lightdirecting device, in this instance, prism 44, is located within thatairgap 60 and receives a beam of polarized light from polarizer 48B.Such polarized beam of light is then further rotated within prism 44,(in accordance with the magnetic field which is created by the magneticconcentrator 54A from current in cable 12), by Faraday effect, thus,providing much output information concerning current in cable 12, aspolarized light to polarizing beamsplitter 50C from which two polarizedlight beams are provided to optical fiber light connections 50A and 50B.

Optical fibers 68A and 68B connect to receive the two output light beamsof polarizing beamsplitter through fiber light connections 50A and 50B,without any optical sensor or amplifier. Of course, optical sensor oramplifier may be used, but it is preferred that nothing but simpleoptical fiber light connections 50A and 50B connect the optical fibers68A and 68B to receive the outputs of polarizing beamsplitter 50C. Theoptical signals received from polarizing beamsplitter 50C, provides twopolarized light beams which are strong enough to transmit through suchoptical fibers 68A and 68B to light detectors 50D and 50E, shown in FIG.9.

Optical fibers 68A and 68B carry the output light beams to be turnedinto electrical signals by light detectors 50D and 50E at the input ofthe electronics system 10, as shown in FIG. 9. Such output informationcontained in optical fibers 68A and 68B because of the dynamiccharacteristics and ability of the magnetic concentrator 54A and greatsensitivity and dynamic ability of electro-optical light directingdevices, such as prism 44, includes a myriad of information concerningthe current quality, including, but not limited to, current level,spectral content, harmonics, stray frequencies, transients, surges andspikes. Impedance and power factor may also be determined if voltageinformation is available.

Due to saturation, in the past, magnetic concentrators, which readilysaturate, have limited the dynamic range of current sensing. An electricutility company has various requirements for the dynamic range ofcurrent to be measured, depending on the application. For example, thenormal operating range would be from at least as low as approximately 5amperes to about 600 amperes and a fault ranges of 10 time the normaloperating range and, even, up to about 40 times the normal operatingrange. At those ranges, a ratio, or scaling, is required. Opticalcurrent sensing together with detection (changing “light” to electricalsignals) provides ready ratio conversion, which is easily changed toanother ratio, as necessary. The industry has agreed that a currentratio of about 100 amperes to 1 volt may generally be used, for normaloperating range, which would allow 1000 amperes to be measured withoutdistortion. However, for fault detection, a greater current ratio, say,1000 amperes to 1 volt, measured in real time, would be required. Ofcourse, rather than trying to fit excessive current into a rangemeasurement system, a simple detector indicator could be used todetermine and indicate when the current has exceeded 1000 amperes. Someother selected excessive value may be used as a maximum if required.This information could be provided, simply, when current exceeds thevalues within the normal current range or ranges.

On the other hand, scaling may, in effect, be determined, very simply,by a system that has a wide current sensing capability and theelectronics system, particularly the computing device, merely utilizingthe data pertaining to the current range of interest.

Wide ranges of core material are available and are commonly used formagnetic fields. Iron by itself, of course, has high permeability, butsaturates at too low of a current level to be used for a wide range ofsensing and measuring.

In a preferred embodiment of the magnetic concentrators herein, highsaturation level is achieved by the magnetic concentrator 54 beingcompressed powder core comprised of magnetic particles dielectricallyinsulated from each other in a dielectric matrix and wherein there areminute distributed airgaps within the powder core. The powder core maybe comprised of various magnetic powders. Some of such powders areiron-containing particles, silicon iron-containing particles, siliconsteel-containing particles, and other mixtures, alloys, and compounds ofiron and steel. Other magnetic materials may also be found useful insuitably raising the saturation level of the magnetic core twice and,even to as many as ten times, the normal current level of the system.

For lower current measuring, higher permeability cores are used and forhigher current measuring, lower permeability cores are used. Suitablemagnetic cores may also be constructed, for example, of laminations ofsilicon steel held together by one or both of an adhesive or an epoxy,or other suitable matrix. Smaller, narrower, lamination strips areuseful for efficiency at higher frequencies of current detection andlarger, wider, lamination strips are useful for lower frequencies ofcurrent detection. Laminations made of powdered core materials are alsouseful.

Narrow hysteresis curves in the magnetic concentrator are desirable andwill substantially reduce the power losses and the measurements will bemore linear, leading to more accurate measurements.

FIG. 6 is a cross-sectional view of laminated, magnetic concentrator 54which includes numerous short, magnetic strips, laminations 64, arrangedin laminar form. The laminated version is of at least one type ofmagnetic material mixed with at least one type of non-magnetic material.The laminations 64 are arranged to create the airgap 60. The mixedmagnetic material greatly increases the saturation level of the magneticconcentrator 54, (the ability to portray high levels of current), whilemaintaining an acceptable sensitivity to low current. Thus, moreeffective use is made of the wide range of capability of optical currentsensors such as optical current sensor 40. Of course, at low currentlevels, because of the low magnetic levels, steps may have to be takento exclude extraneous magnetic fields by shields, screens or otherwise.

The magnetic concentrators 54 and 54A, in FIGS. 5A, 5B and the next Fig,FIG. 6, are low in cost, may be easily clamped onto existing cables 12without cutting the cables 12, and provide a better dynamic range incomparison to prior art solutions.

The embodiment of FIG. 6, the magnetic concentrator 54 is shown asC-shaped. This allows the use of laminations and more standardcomponents. The FIG. 6 embodiment further includes a hinge 59 to allowthe magnetic concentrator 54 to open up and facilitate installationaround a current carrying cable, without disruption of the cablefunction.

While three embodiments of different shape magnetic concentrators aredisclosed in FIGS. 5A, 5B and 6, the magnetic concentrator may be of anyshape that functions to provide the necessary magnetic field to anairgap within which an optical current sensor can be placed.

By properly selecting the magnetic concentrator 54 and adapting theelectronics, the sensors can be used for multiple applications. Forexample, assume a 600 ampere nominal current sensor 40 is capable ofmeasurement of very high momentary fault current (e.g., approximatelyequal to or greater than 5,000 amperes). The electronics are fast, highin bandwidth, but lower in gain and accuracy at that level. For currentless than 1 ampere it is desired to measure at a lower bandwidth forseveral reasons. A normal harmonic content should be less than 5% and 5%of 1:600 ampere is negligible (0.000083 ampere) for metering and forquality of power. Therefore, a bandwidth of about 200 Hz is acceptableat this current. Current state of electronics allows dynamic adjustmentof the gain and the bandwidth. The system disclosed is capable offiltering, through the use of filters or by computer data processingand, thus, is able to provide information down to 0.1 Hz.

The lower limit is the noise floor of the signal being processed, whichis determined mostly by the source of the beam(s) and of theelectronics, and the higher limit is the current at, or just below,saturation of the magnetic concentrator 54 and the power supply levelsof the electronics.

Although a voltage sensor is not included in this application, opticalfiber 100 may be made available to provide an input light beam, from aLED or laser, (which components are well-known in the art), to thevoltage sensor area 78 shown in FIG. 7D. Optical cables 102A and 102B,FIG. 7B, provide the outputs from any voltage sensor placed in suchvoltage sensor area 78.

Thus, by the use of optical fibers, the electronics components may belocated remotely from the high voltage cable, such that deterioratingeffects of high voltage transients, lightning and other weatheringconditions on the electronics parts can be reduced.

If a laser is used as the light source 48, the light beam produced bythe laser will likely need to be depolarized and then collimated inorder to be suitably polarized at the input to the light directingdevice, prism 44. If a LED is used as the light source 48, the lightbeam produced will need to be collimated in order to be suitablypolarized at the input to the light directing device, prism 44. Ofcourse, other light-emitting devices which are found suitable, may beused.

From the standpoint of overall management of an electrical distributionsystem, its safety, efficiency, reliability, and economics, determiningthe quality of current is of prime importance. Current quality includesdetermination of one more factors of current level, spectral content,harmonics, transients, impedance, surges and spikes and power factor.Determination of impedance and power factor would require someinformation as to voltage, including time of zero cross-over.

Computing devices (computers, digital signal processors,microprocessors, and the like), receiving information through theoptical fiber cables, can readily provide the necessary evaluation andmathematical analysis to determine such factors of quality fromelectrical signals representative of current, (and, in the case ofimpedance and power factor some information as to voltage).

Of course, input from a voltage sensing system would provide additionaldesirable information about the quality of electricity being deliveredby the distribution system. A voltage sensing system provides goodcapability for analyzing harmonics, transients, spikes and voltageanomalies in the system.

For assessment of power quality, the measurement of harmonics and otherfrequencies in the current is critical, so higher bandwidths, such as 45Hz to 6000 Hz may typically be required. This is readily achievable inthe system disclosed herein.

Smart grids deliver electricity from suppliers to consumers usingdigital measuring and monitoring technology to save energy, reduce cost,and increase reliability and transparency of grid conditions. With suchsmart grids, utilities and industrials will require that the same sensorbe used for multiple ranges and purposes. Programmable gain amplifiersand variable filters controlled by a computer and frequency analysiswithin the computer itself, as taught herein, can optimize theinformation provided by the optical current sensor, as to current level,spectral content, harmonics transients, faults and other quality ofpower factors and analyze, evaluate and otherwise process and providesuch information.

Thus, valuable additional information as to quality is provided.

Considerable information concerning harmonic measurement and analysis inpower systems is found in IEEE Transactions On Instrumentation andMeasurement, Vol. 55, No. 3, June 2006, article by Slobodan J.Petricevic, et al. Such information includes improving the sensing head,airgap, and frequency response and the harmonic analysis algorithm of awaveform.

Of course, in doing harmonic analysis, frequency selection and bandwidthselection the computing device 130, FIG. 9, is very capable. It may, forexample, use filtering techniques, Fourier analysis, discrete Fouriertransform (DFT), fast Fourier transform (FFT), and other analyticaltechniques well-known to those skilled in the art, to determine spectralcontent, harmonic, transients and other frequency content of electricalsignals. This capability is in addition to the capability of thevariable filters or fixed filters whichever may be also used.

FIG. 7A is a side elevation view of a revised version of the opticalsensor assembly 10, using an alternative mechanical structure of clamps29 and housing 30 and the alternative embodiment of magneticconcentrator, (not visible), that is shown in FIG. 5B. The magneticconcentrator and its housing 30 are in closed position and the exteriorof the optical sensor assembly 10 is shown. Housing 30 opens and closesby being connected through a pivot 36 to an upright panel 37 on flange39 which furnishes a mounting base for the upper elements of opticalsensor assembly 10. Under flange 39 lies a collar-like top end 22 oflower base unit 20. Flange 39 and top end 22 are electrically connectedand are electrically conductive of the voltage on cable 12 when theoptical sensor assembly 10 is clamped to such cable 12. Clamp 29, whichis adjustable by locking element 38, is shown clamped on cable 12,holding it firmly with respect to the optical sensor assembly 10. Thereare two of such clamps 29, one on each side of housing 30. The secondclamp 29 on the far side is not visible in this view.

There is shown an exterior covering 21 of a high dielectric shieldingmaterial of rubber, silicone rubber or other suitable high dielectric asdiscussed previously in connection with FIGS. 3 and 4. Such exteriorcovering 21 has a number of outer flanges 23, as previously described,which increase the exterior arcing path.

At the bottom of the optical sensor assembly 10 is shown a pass-throughconnector 25, through which the optical fibers and any other necessaryor desirable light or electrical conductors may pass. Ground stud 82 isalso shown.

FIG. 7B is a front elevation view, of the optical sensor assembly 10showing several optical fiber cables 27 which are connected to pass intothe interior of the optical sensor assembly 10. Both clamps 29, onopposite sides of housing 30 are shown.

Optical fiber cables 27 includes optical fiber cable 66 for providinginput light to the light directing device, (prism 44, in thisembodiment, see FIG. 5B), of optical current sensor 40, and opticalfiber cable 68A and 68B for providing the output from the opticalcurrent sensor 40 to the electronics system 104 of FIG. 9. Provision ismade for inclusion of a voltage sensor, see FIG. 7D, by providing inputlight to the voltage area 78 on input optical fiber cable 100 and outputis received from such a voltage sensor, if one is included, on outputoptical fibers 102A and 102B.

It appears that a multi-mode optical fiber works well for transmittinglight from an LED light source. A single-mode fiber works well fortransmitting light from a laser light source.

Of course, if an optical fiber is to be used to carry polarized light,it must be of a type that maintains that polarization. Polarizationmaintaining optical fibers are readily available commercially.

FIG. 7C is an isometric, frontal view of the optical sensor assembly 10,illustrating the magnetic concentrator housing 30 open and, thus, themagnetic concentrator 54, within the housing 30 is also open. The cableclamps 29 are shown. Optical fiber cables 27, extending from the bottomof the optical sensor assembly 10, are also shown.

There is also shown another housing 33 disposed on and firmly attachedto flange 39. Such housing 33 has within it, two spaced apart segments54B and 54C, (not visible, but visible in the next illustration FIG.7D), of the magnetic concentrator 54, with an optical current sensor 40,(not visible, but visible in the next illustration, FIG. 7D), disposedin the space between them. Such space is the airgap 60, (not visible,but visible in FIG. 5B), of the magnetic concentrator 54.

FIG. 7D is a side elevation, partial cross-section view of the opticalsensor assembly 10, illustrating the interior thereof. The opticalfibers entering the assembly 10 at 25 and extending up through channel72 and connecting to optical current sensor 40 are not shown. Inoperation, with the optical sensor assembly 10 clamped to a currentcarrying cable 12, the housing 30 and magnetic concentrator 54 therein,are pivoted into closed position, as shown, and are locked in place toflange 39 by locking element 38.

Magnetic concentrator 54 has two additional lower magnetic segments 54Band 54C which continue the magnetic field created by magneticconcentrator 54 and which form an airgap between them. Optical currentsensor 40, or, at least prism 44 thereof, is disposed within such airgapand any polarized light passing through optical current sensor 40 isexposed to the magnetic field in that airgap between the magneticconcentrator segments 54A and 54B.

A light beam, (from a LED, laser, or other suitable light source, aspreviously and hereafter described), is brought into the optical sensorassembly 10 by means of one of the optical fibers in optical fibercables 27, (not shown, but see FIG. 7C), that enters the bottom of theoptical sensor assembly 10 through pass through connector 25 and whichoptical fiber cables 27 pass on up through centrally locatedelectrically conductive channel 72 which may be made of aluminum,stainless steel or other conductive material, such as, but not limitedto, metallic screen/mesh or one could chemically or mechanically apply ametallic coating to said cables 27 for the desired length.

Conductive channel 72 is electrically attached to collar-like, top end22, which is likewise conductive and which, in turn, is connected toelectrically conductive flange 39, which is connected electrically tocable 12. Of course, other connections may be used to electrifyconductive channel 72.

Conductive channel 72, which is preferably a tube, protects the opticalfiber cables 27 running therethrough from high electrical e-fields andthe associated stresses.

Silicone gel is one of many suitable dielectric sealants known to thoseskilled in the art for use in high voltage equipment. The sealants areapplied to avoid voltage breakdown. Wherever there is a high voltagegradient such high voltage sealants may well be used to preventshort-circuit breakdown.

The optical fiber cables 27, (seen in FIG. 7C), has therein an inputoptical fiber 66, seen in FIG. 7B, which has a polarized light beamtherein, provided by a light source located in the electronics system104. See FIG. 9.

In FIG. 7D, optical fiber cables 27 includes input optical fiber 66which enters into the optical current assembly 10 through connector 25and passes up through conductive channel 72 and provides an input beamof light to optical current sensor 40. Such beam of light may or may nothave been polarized and/or collimated or otherwise conditioned, asnecessary or desirable. If the beam of light is not yet polarized, it ispolarized at the entrance to optical current sensor 40. While in opticalcurrent sensor 40, especially in prism 44, thereof, the polarized lightbeam is exposed to the magnetic field of airgap 60, (see FIG. 5B), whichcauses, by Faraday effect, rotation of the polarization of the lightbeam in accordance with the current flowing in cable 12. Such light beampasses through and on out of optical current sensor 40 as two lightbeams, having, preferably, passed to output through a polarizingbeamsplitter, (not visible, but see FIG. 10, for an example), withinoptical current sensor 40. Optical fiber cables 27, includes two outputoptical fiber cables, 68A and 68B, see FIG. 5B, which carry such tworotated, polarized light beams back down through centrally-locatedconductive channel 72 to leave the optical sensor assembly 10 at thebottom and proceed to light detectors 50D and 50E, (see FIG. 9), forchanging the light beams into electrical signals for further evaluation,analysis and data processing.

Within the central portion of the optical current assembly 10 is adielectric housing 73 which provides rigidity and dielectric soundness.Empty area 75 is encased within a conductive metal tube 77 made fromstainless steel, aluminum or other suitable material which iselectrically grounded by ground stud 82. Such tube 77 extends upwardfrom the bottom of the optical sensor assembly 10 until it reaches anarea in proximity to the level occupied by conductive channel 72, whichcarries the voltage potential of cable 12. Thus, there is a voltagefield space 78 created between grounded tube 77 and conductive channel72 within which a voltage sensor, (none shown), may be inserted andconnected.

FIG. 8A illustrates an arrangement for the optical sensor assembly 10according to an embodiment of the disclosure, wherein the optical sensorassembly 10 is suspended from the cable 12 in a high voltage electricitydistribution system, and is connected to an electronics system 104 forcontrol and/or other evaluation of the current and voltage levels, (if avoltage sensor is included), by means of fiber optics cables 66, 68, 100and 102. An electrical ground is shown obtained by connection 83 to aground pole of the electricity distribution system. Of course, anelectrical ground may be obtained in many other ways and places.

As illustrated, the output optical fiber 68, (which likely is actuallytwo optical fibers, 68A and 68B,) contains current information which isprovided to the electronics system 104, which includes a computingdevice 130, (not shown, but see FIG. 9) which may be a microprocessor,computer, digital signal processor, (DSP), or the like.

Similarly, optical fiber 100 provides a beam of light from a lightsource in the electronics system 104 to a voltage sensor, (if one isinstalled), in voltage field space 78, FIG. 7D. Optical fiber 102 (whichmay well be two optical fibers 102A and 102B, FIG. 7B, because of beamsplitting), provides light information as to the output of a voltagesensor, if included, to the electronics system 104, for processing.

The output of electronics system 104 may be fed to a relay or remoteterminal unit 106 for transmission to other systems, if desired, some ofwhich are listed next to relay or remote terminal unit 106. One of suchsystems, for example, might be a recorder with time labeling orstamping. Various capable recorders are commercially available for fastrecording of date and information and further analyzing such data andinformation. Interface is easily made to products, such as Telvent,Elspec and other products, of other companies.

Other configurations are also possible, as illustrated in FIGS. 8B-8D.In the embodiment of FIG. 8B, the electronic system unit 104 isconnected through isolating converter 108 to the relay or remoteterminal unit 106 which may interface with various other companyproducts having various capabilities pertaining to the data andinformation created by electronics system 104.

In the embodiment of FIG. 8C, the relay or remote terminal 106 is showninterfacing with possible additional product lines. In the embodiment ofFIG. 8D, the electronic system 104 is operably attached to wirelessdevices such as radio 110 using RS232 telecommunications standard and/orEthernet connected device 112, a device that would 5 implement and usenetworking standards. Therefore, the output data may be provided informat or protocol for use in either wireless or wired communications.

FIG. 9 is one example of an electronics system 104 shown in FIGS. 8A, B,C and D, wherein the light detectors 50D and 50E, (which may bephotodiodes or other light sensitive devices), of the light analyzer 50(see FIGS. 5A and 10), are located remotely from the optical currentsensor 40, in or near the electrical system 104. However, it would bepossible to put such light detectors at or near the optical currentsensor 40, but, preferably they are located as shown, at or near thedata processing capability of the electronics system 104.

FIG. 9 also is a schematic diagram of one embodiment of the electronicssystems 104 of FIGS. 8A-8D, which systems process, analyze and evaluatethe information as to the current in the cable and provides outputstherefrom. FIG. 9 includes a device such as a computing device, adigital signal processor or a microprocessor or the like; FIG. 9 is oneexample of an electronics system 104 wherein the two beams of polarizedlight received on optical fibers 68A and 68B are detected and turnedinto electrical signals by light detectors 50D and 50E, which are shownas photo-diodes, but which may be any suitable detector for turningpolarized light into electrical signals.

The light detectors 50D and 50E are the remaining elements of the lightanalyzer 50. See FIG. 10.

In FIG. 9, such light detectors 50D and 50E may handle multiple channelsif they are multi-frequency capable. The embodiment shows such lightdetectors 50D and 50E as being “photodiodes” but they may be other lightsensitive components such as, but without limitation, photo resistors orphoto transistors.

In FIG. 9, the electrical signals from the light detectors 50D and 50Eare connected through programmable gain amplifiers (PGAs) 122 andthrough other more direct channels such as 123A and B and 125A and B toanalog to digital converters 126.

It is noted that temperature information is received from a temperaturesensor 137, illustrated hereafter in FIG. 10, placed near the prism 44,(which is somewhat sensitive to temperature), provides temperatureinformation which can be used, for example, in the computer in a“look-up” table or in a formula or otherwise, to correct the readings ofprism 44 which may be affected by temperature at the site of the currentmeasuring.

A desirable feature, protective to both customer and distributionsystem, is to disable or disconnect, say, the main circuit breaker orselected portions of the customer's system or the distribution system,or any combination of them, upon detection of excessive current orexcessive voltage by either the described electronic system of FIG. 9,or by separate excessive current detecting devices and excessive voltagedetecting devices or by both. No such separate excessive currentdetecting system is shown, but components thereof are readily availablecomprising an excessive voltage sensor, a trip relay and a circuitbreaker. Information concerning the relative timing of events is oftenvery valuable and such measurement is considered one of the mostimportant measurements in power utility grid control. The informationthus provided gives better event detection and location, prediction ofgrid instability, reduction of blackouts, better load control such asdesirable load shedding, isolation of inoperative areas, early detectionof faults, prevent of blackouts and other evaluations that improve thequality and reliability of the power utility grid.

It is noted in FIG. 9, that a clock 138, in addition to the computer'sown internal clock, is included in the electronics system 104. This isdesirably included, (whether within or outside of the electronics system104). Clock 138 is much more accurate than the standard microprocessorclock within the electronics system. Clock 138 is desirablysynchronized, say, by satellite, (such as the Global Positioning System,(GPS)), with a reliable external time reference or otherwisesynchronized to a standard source. In this manner, there could beprovided and recorded a running time stamp for all events of interestbeing measured, analyzed or evaluated by the system. Of course, suchclock 138 must have an independent, reliable source of power.

With such a clock 138 and continuous, accurate time informationtherefrom, a time stamp could be added to the signal or record of everyevent down to nanoseconds, but, inasmuch as it is running continuously,it may provide time indication for any event or interval desired. Acontinuous time stamping of data could be provided, if desired. If, forexample, recording is done, as is often the case, of the output of theelectronics system 104, or portion thereof, a time stamp of any events,or all events, may be recorded and preserved, from information providedby clock 138. A less accurate clock may also be included to give abroader, more general view of the sequence of events that are not ofhigh frequency or short duration.

Also, within electronics system 104 is a light source 48, which may ormay not be a polarized source, provides a beam of light, (probably in ornear the near infrared frequencies, but not necessarily so), to opticalfiber 66 which transmits it for use in current sensor 40, shown in FIG.5A and FIGS. 10-12. Such light source 48, or an additional light source,may provide a beam of light for a voltage sensor, on output opticalfiber 100, if a voltage sensor is included in the system. Dotted line139 indicates a possible communication link, possibly with communicationin both direction for better control, between the computing device 130and light source 48 which would allow computing device 130 to controlthe light source 48, depending on its capabilities, as to one or morefrequencies, one or more power output levels and as to any desiredmodulation of phase, frequency, amplitude, square wave, pulse, or otherform of modulation.

In FIG. 9, the amplification channels may be divided into many channelsin order to differentiate between the AC and DC components of the beamor to accommodate more than one sensor. In the present embodiment, theelectronics 104 includes a first channel 123 and a second channel 125.Additional channels may also be included, within the present skill ofthose knowledgeable in the art. Also, as shown in FIG. 9, additionalchannels, such as 123A and B and 125A and B, around the PGAs 122 andfilters 124, may or may not be included.

Channels 123A and 125A provide raw, AC electrical frequencies in thedetected light beam, directly to analog to digital converters 126.Channels 123B and 125B provide raw, integrated, or smoothed, electricalfrequencies in the detected light beam, directly to the analog todigital converters 126. Thus, additional information concerning thecurrent flowing in the current carrying cable 12 is furnished directlyto the computing device 130, through analog to digital converterconverters 126, to be used in the digital processing of information.

The PGAs 122 may be of a type that receive commands from a computer bus.The commands may be bus discrete commands, such as by changing aresistor or voltage (as is 30 done with a Voltage Control Amplifier) orcurrent command or otherwise. This programming of the gain may becompared to Automatic Gain Control (AGC) as in the art of radio. ThePGA's 122 may include low pass or band pass filters or variable bandpass filters connected to separate filters 124. The filters 124 orfilters which may be located within or near the PGA's 122 may includepassive and/or active components. The filtered signal is directed to ananalog to digital converter 126 that sends the digital signal to thecomputing device 130, which is a digital signal processor or amicroprocessor or a computer or the like.

The symbols within computing device 130 indicate, in a general way, thecapabilities of the computing device 130 to analyze an electrical wave,electrical waves of several frequencies, (including harmonics and strayfrequencies) and to integrate, smooth or average the information.

In a preferred embodiment, the analog to digital converters 126 sampleat 15 kHz. Using anti-aliasing filters of 5.64 kHz, (not illustrated) atthe input to the programmable gain amplifiers 122 or, possibly, at theinput to the analog to digital converters 126, the computer is enabledto determine harmonics and other frequencies up to the 53rd harmonic ofa 60 cycle power distribution system. This enables comprehensiveinformation concerning the spectral content and other quality factors ofthe current being analyzed and evaluated. A common requirement isinformation as to frequencies up to 15 kHz.

The computing device 130 controls one or more of gain, frequency,bandwidth or other filter capability, based on the received signal andthe program installed on the computer. Computing device 130 controls thePGAs 122 and the filters 124, accordingly. The analog to digitalconverter 126 may include a separate analog to digital converter foreach channel 123 and 125, or may include a single multi-channel analogto digital converter.

Scaling of current levels to be measured is easily accomplished by thecomputing device 130 changing the gain and bandwidth of the filters 124and/or the programmable gain amplifiers 122, by control or by filteringwithin the computing device 130 or in other ways.

Also, for frequency analysis, fixed frequencies filters, either activeor passive, in multiple channels, to the extent desired, may be locatedbetween the programmable gain amplifiers 122 and the computing device130 in order to pass predetermined frequencies or bands of frequenciesof interest.

The output information from electronics system 104, from computingdevice 130 may, for example, without limitation, feed an output to adigital to analog converter 132, and those analog electrical signals maybe amplified by an amplifier 134 for further evaluation, analysis orother usage. In addition, computing device 130 may feed information to adigital communication network 136 for further distribution and usage ofthe information as previously explained in FIGS. 8A, B, C and D.

The electronic system 104 can be interfaced through analog or digitaloutputs. In one embodiment, the analog output can be a low energyoutput. For example, a ratio of 10,000:1 may be used for voltage, inthis case 7200 volts on the cable 12 will be represented by 0.72 volts.See FIG. 8C. Other ratios can be provided. A current may also berepresented by a voltage. For example, 500 amperes may be represented by1 volt. This low energy analog interface will be generally connected toa Remote Terminal Unit (RTU), as shown in FIGS. 8A, 8B and 8C anIntelligent Electronic Device (IED), a Programmable Logic Controller(PLC), a Supervisory Control and Data Acquisition System (SCADA), or arelay or remote terminal unit 106, to send the information to a controlsystem.

There may be cases wherein the optical sensor assembly 10 may be usedfor more than one application. For example, the assembly 10 maysimultaneously be used for fault location together with regulating thequality of power. If necessary or desirable, more than one channel ofanalog to digital conversion may be used. The analog to digitalconversion can be done by more than one analog to digital converters ora multichannel analog to digital converter. This “multi-channel gain”approach can also be implemented by software instead of hardware.

When legacy equipment is interfaced with the sensors, such as revenuemeters or old relays, power amplifiers may be added (to mimic instrumenttransformers) to the analog output. A typical voltage to a meter in theUnited States is 120 volts, so a ratio of 60:1 will provide 120 voltswhen the cable 12 has 7200 volts. Other voltages up to 1,000 volts areavailable. A voltage to current amplifier may be connected to the analogoutput; for example, a 600:5 ampere ratio is typical in the UnitedStates.

For more modern smart grid applications, the digital output may be used.The most common are the RS-232, (wireless), and/or the Ethernet (wired).As shown in FIG. 8D the computing unit 130 may be programmed to utilizewhichever is the standard protocol in the customer region.

FIG. 10 is an illustration of a light source 48A and a polarizer 48Bproviding polarized light 52 which passes into reflective prism 44 andis reflected as shown by light beam 52A where it is then affected by themagnetic field, due to the Faraday effect. The polarization of the lightbeam, in a preferred embodiment, is orthogonal to the magnetic field asshown by line 52D representing the polarization direction ofpolarization of light beam 52A at an angle of 45 degrees upward from thetop plane of prism 44, (which is parallel to the plane of reference forthe beam 52A within prism 44), as can be seen with reference to dottedline 44A which lies parallel to the plane of the top of prism 44. Thepolarized light beam 52A is rotated in its polarization by magneticfield H, but stays orthogonal to magnetic field H as can be seen in thedrawing. In other words, the 45 degree angle increases or decreases,caused by the Faraday effect of a magnetic field on polarized light.Subsequently, the rotated, polarized light beam 52A is reflected intolight beam 52C which then passes out of the prism 44 to optical fiberlight connections 50A and 50B of light analyzer 50. The outputinformation is then sent to the electronics system of FIG. 9 on opticalfibers 68A and 68B.

The light analyzer 50 is connected to receive said rotated, polarizedlight 52C output and provide electrical signals representative of thecurrent flowing in said cable. In the embodiment shown the lightanalyzer 50, (which is shown, except for the light detectors 50D and 50Eincluded remotely at the input to the electronics system 104 shown inFIG. 9), is comprised of a polarizing beamsplitter 50C which providestwo output polarized light beams containing a myriad of informationconcerning current in cable 12. Optical fibers 68A and 68B are connectedto receive the two polarized beam outputs from polarizing beamsplitter50C, by optical fiber light connections 50A and 50B. Optical fibers 68Aand 68B transmit the two polarized beam outputs to light detectors 50Dand 50E, for conversion into electrical signals as can be seen at theinput to FIG. 9.

In FIG. 10, the polarizing beamsplitter 50C is disposed at 45 degrees tothe prism 44. Of course, the polarizing beamsplitter 50C may beconstructed as a single device or as two devices, a polarizer and abeamsplitter. The term “polarizing beamsplitter” is intended to coverboth a combined device and two separate devices.

Other light analyzers may be used, such as those involving polarizers,beam splitters, quarter-wave plates, half wave plates, sensors,photodiodes, photo transistors, and other light analyzer and detectormeans known to those skilled in the art.

Preferably, the light detectors 50D and 50E, which are part of lightanalyzer 50, are located remotely from the main body of optical sensorassembly 10. In FIG. 9, light detectors 50D and 50E are shown remotelylocated in the electronics system 104.

The accuracy and the range of light directing devices, such as prism 44,are often influenced by temperature. The accuracy and range of measuringby prism 44, and, of course, various other suitable light directingdevices, is increased substantially by temperature compensation.Consequently, a temperature sensor 137, placed in proximity to the prism44, (or any other light directing device which may be used that istemperature sensitive), provides information as to the temperature ofthe prism 44 which information is fed to the computing device 130 asshown in FIG. 9. A previously determined look-up table of compensation,a mathematical formula, algorithm or other method, within said computingdevice 130 may be used to correct the output information of the lightdirecting device and, thus, substantially extend the capability of thelight directing device. In some instances, of course, calibration may beused. Numerous temperature sensors are readily available, using solidstate devices, bimetallic devices, resistor-based devices and many othertemperature sensing techniques. A popular one is to coat the tip of anoptical fiber with a fluorescent paint that changes color withtemperature. A photodiode then reads the color, and, thus, thetemperature, of the fluorescent paint. A suitable range of a temperaturesensor would be from −50 degrees C. to 100 degrees C., with an accuracyof 1 degree and a response time of, say, less than a minute. The rangeof frequency detection by the light directing device is much improved bytemperature compensation.

It will likely be desirable to improve the internal reflection bycontrolling the refractive index of the adjoining material, (on thereflective surface or surfaces of the light directing device, prism 44in this embodiment). One such method is to place “caps” on the outerside of the reflective surfaces of reflective, light directing devicesentrapping a gas of known refractive index. The temperature coefficientof expansion of the cap must be closely related to the temperaturecoefficient of expansion of the light directing device. Thus, for aglass prism, the cap could be of the same material as the prism.Plexiglass, Ultem, a commercially-available resin, which may beglass-filled, and other materials may be found suitable in particularapplications. The cap might be formed in the shape of, say, a bakingpan, turned upside down and glued to the outer side of the reflectivesurface. The space within the cap may include, for example, but notlimited to, nitrogen, argon or a hygroscopic material and trapped dryair.

FIG. 11 is an illustration of polarized light 52 passing twice throughlight directing device, prism 44. As seen by light beams 52A and 52B,the polarization of output light beam 52C will be doubly affected by theFaraday effect, caused by the magnetic field H. Inasmuch as thepolarized light has traveled twice through prism 44, light 52A and 52Bin opposite directions, miscellaneous “non-ideal” responses of the lightdirecting device, prism 44, will be removed from the output signal.

FIG. 12 is another illustration of an optical current sensor 40, showinga light source 48A, a polarizer 48B and, thus, polarized light 52 passesthrough the reflective prism 44, to be affected by the Faraday effect ofa magnetic field H. The light passing out of the reflective prism 44 toa polarizing beamsplitter 50C is then turned into electrical signals bythe light analyzer 50. In this instance, the light detectors 50D and50E, which turn light signals into electrical signals, are located at ornear the light directing device, prism 44 and the outputs of lightdetectors 50D and 50E are electrically connected to electrical channels123 and 125. See the relation of those two electrical channels 123 and125 in FIG. 9.

It is recognized that FIGS. 10, 11 and 12 show the light and the lightpath in somewhat schematic form. A quick understanding or visualizationof a beam of light and the light path in traveling through a translucentmedium may be seen in FIG. 1, of U.S. Pat. No. 5,939,711 forElectro-optic Voltage Sensor Head. Such patent, although it involves“Pockels effect,” a voltage field effect, instead of “Faraday effect,” amagnetic field effect, is helpful in illustrating in FIG. 1, the passageof a beam of light through a translucent medium.

As may be seen in FIG. 12, the light source 48A may be located at ornear the optical current sensor 40. On the other hand, the polarizedlight source may be located remotely and the light may be sent tooptical current sensor 40 by fiber optic cable 66 as shown in FIG. 5A.

Similarly, the light detectors 50D and 50E, of light analyzer 50, inthis embodiment are located at the output of the beamsplitter andpolarizer 50C, close to the light directing device, prism 44.Alternatively, of course, the light detectors 50D and 50E may be locatedat a distance through the use of optical light sensors and opticalfibers at the output of the beamsplitter and polarizer 50C. Such opticalfibers would then be connected to the remote light detectors 50D and50E.

FIG. 13 is an embodiment of a light directing device, prism 44, inlinear form, receiving light through an input polarizer 48B andreflecting it through the light directing device, prism 44, wherein itis rotated by exposure to a magnetic field H. The light then travels toan output comprised of an output polarizing beamsplitter 50C. The twooutput polarized light beams are optically connected by optical fiberlight connections 50A and 50B to optical fibers 68A and 68B, whichoptical fibers transmit them to light detectors 50D and 50E, forconversion into electrical signals as shown at the input to FIG. 9.

FIG. 14 is an embodiment in which the input polarizer 48B and the outputpolarizing beamsplitter 50C are located in line with the light directingdevice, prism 44. The input polarizer 48B reflects the beam of lightinto the light directing device, prism 44, wherein it is exposed to amagnetic field H and then it is reflected from the light directingdevice, prism 44, by a polarizing beamsplitter 50C into optical fiberlight connections 50A and 50B and thence through optical fibers 68A and68B to light detectors 50D and 50E for conversion into electricalsignals as shown at the input to FIG. 9.

FIG. 15 is an embodiment in which the input light enters the lightdirecting device, prism 44, without reflection, through an inputpolarizer 48B, and such light is then exposed to a magnetic field H andis then reflected out of the light directing device, prism 44, by anoutput polarizing beamsplitter 50C to optical fiber light connections50A and 50B and thence through optical fibers 68A and 68B to lightdetectors 50D and 50E, for conversion into electrical signals as shownat the input to FIG. 9.

A voltage sensor, a sensor sensitive to Pockels effect, may be placed inthe voltage field of the cable 12, as explained in connection with FIG.7D, may be used in conjunction with this current sensing system toprovide additional information about the system's condition.

FIG. 15 is intended to illustrate the polarizers and the beam splitteras distinct elements from the light directing device wherein suchelements are adjacent to the light directing device. However, FIG. 15 isalso intended to illustrate another embodiment of the light directingdevice in which one or more of the polarizers and polarizer beamsplitterare integral with the light directive device. Such integration may beaccomplished as to bulk glass and various other light directive, orlight transmissive, devices.

FIG. 16 is a functional block diagram of an optical sensor assembly 240for measuring a characteristic of electricity, such as current, in acurrent carrying cable, such as the current carrying cable 12. Theoptical sensor assembly 240 includes an input light polarizing element248, which has a low Verdet constant and receives an incoming light beam202 from the light source 48A. The input light polarizing element 248produces a polarized light 252 at its output. The optical sensorassembly 240 further includes a prism 244 mounted to the input lightpolarizing element 252. The prism 244 receives the polarized light 252and has a first reflective surface 262 positioned immediately adjacentto the input light polarizing element 248. The prism 244 has a highVerdet constant relative to the low Verdet constant of the input lightpolarizing element 248. The distance, d, shown in FIG. 16, between thesloped, reflective surface 262 and the input light polarizing element248 having a low Verdet constant is as close to zero as possible so thatthe polarized light 252 entering the prism 244 along the y- orz-direction travels as short a distance as possible through the highVerdet constant material before traveling across the airgap 60 along thex-direction. Within this distance, the polarization angle of thepolarized light 252 as it travels orthogonal to the x-direction of themagnetic field of interest BX can be undesirably influenced by magneticfields from another nearby current carrying cable other than the currentcarrying cable 12 to which the optical sensor assembly 240 is coupled.Thus, it is desirable for the distance, d, to be as close to zero aspossible to minimize the distance that the polarized light 252 travelsin the high Verdet constant medium of the prism 244.

Advantageously, by having a low Verdet constant, the incoming light beamas it travels through the input light polarizing element 248 isrelatively unaffected by unwanted magnetic fields traveling in they-direction, orthogonal to the direction of the magnetic field ofinterest BX, and therefore, less susceptible to such magnetic fields. Ineffect, by shortening all the y-axis or z-axis distances the lighttravels before and after spanning the airgap 60, combined with theselection of a low Verdet constant for materials that the lighttraverses along the y-axis or z-axis and a high Verdet constant formaterials that the light traverses along the x-axis through the airgap,a current sensor having a very wide dynamic range for sensing currentand very low sensitivity to unwanted magnetic fields can be achieved.

While the present disclosure is not limited to specific Verdetconstants, a ratio of the high Verdet constant to the low Verdetconstant can be at least 4:1 or at least 6:1. Stated differently, thelow Verdet constant in an example does not exceed 4 rad/Tm or does notexceed 3 rad/Tm or does not exceed 2 rad/Tm, and the high Verdetconstant is at least 12 rad/Tm or at least 22 rad/Tm or at least 36rad/Tm or at least 40 rad/Tm. The relative terms “low” and “high” inconnection with the Verdet constant of the sensor materials will beunderstood by those skilled in the art of electro-optical sensors.According to the Faraday effect, the angle of rotation of the polarizedlight is a function of the Verdet constant and the optical path length,or the physical distance that the polarized light travels through amagnetic field. The sensitivity of the material is thus related to theoptical path length, so the materials are selected such that the glassprism through which the polarized light travels in the same direction asthe magnetic field of interest has a relatively high Verdet constant andis thus highly sensitive to the magnetic fields. On the other hand,light traveling through other materials that are also exposed tounwanted magnetic fields is passed through a material having arelatively low Verdet constant and is thus relatively insensitive tosuch unwanted magnetic fields. The values and ratios provided herein areexemplary as they are related to the optical path length selected forthe polarized light. The imprecise nature of language renders the terms“high” and “low” difficult to quantify any more precisely than theordinary meaning of the words themselves allows, but persons of ordinaryskill in the art to which the present disclosure pertains willunderstand what these terms mean. For example, a person of ordinaryskill in the art would not understand that a Verdet constant of 1 rad/Tmto be a “high” Verdet constant in the context of the present disclosure.

The first reflective surface 262 changes a direction of the polarizedlight 252 passing through an intermediate portion 260 of the prism 244.The optical sensor assembly optionally includes an output lightpolarizing element 250 coupled to the prism 244. The prism 244 has ahigh Verdet constant relative to the Verdet constant of the optionaloutput light polarizing element 250. An optional second sloped,reflective surface 262 can be positioned at the other side of theintermediate portion 260 to change the direction of the rotated,polarized light 252C before it leaves the prism 244. The slopedreflective surfaces 262 oppose the intermediate portion 260 such thatthe pair of reflective surfaces 262 and the intermediate portion 260form a trapezium shape as shown, for example, in FIG. 21C. Otherwise,the rotated, polarized light 262C can leave the prism 244 without beingreflected and provided to the light analyzer 50 as shown in FIG. 16.

An overall height of the intermediate portion 260 of the prism 244 canbe equal to or no greater than a height of the trapezium. As mentionedabove, as the polarized light 252 travels across the airgap 60 in thehigh Verdet constant medium, the angle of rotation of the polarizationis changed according to the Faraday effect, producing a rotated,polarized light 252C whose angle of rotation bears a linear relationshipwith the electrical current flowing through the current carrying cable12. The output light polarizing element 250 can include one or morerotated, polarized light beam outputs 250A, 250B, which are provided tothe light analyzer 50.

FIG. 16 illustrates an aspect of many aspects pertaining to the presentdisclosure, whose principles, structures, functions, and other teachingsapply equally or equivalently to any other sensor disclosed herein, suchas any sensor 40 shown and described in connection with FIGS. 5A, 5B,and 10-15. The figures represent various exemplary implementations ofthe present disclosure, but they are intended to be merely illustrativeof the aspect shown and described in connection with FIG. 16. ComparingFIG. 17 with FIG. 18, two different orientations of the optical sensorassembly 240 are shown. In FIG. 17, the optical sensor assembly 240 isoriented such that the incoming light beam 202 enters the prism 244 in adirection that is substantially orthogonal to a direction of theelectrical current in the current carrying cable 12. In FIG. 17, theincoming light beam 202 enters the prism 244 along the y-axis direction,while the electrical current flows in the z-axis direction through thecurrent carrying cable 12. Here, magnetic fields, particularly with ay-axis component, designed by BY in FIG. 17, can undesirably influencethe polarized light 252 as it travels through the high Verdet constantmaterial of the prism 244 along the y-axis before it spans the airgap 60along the x-axis parallel to the magnetic field of interest BX. Asdescribed in FIG. 16, by shortening the distance between the input lightpolarizing element 248 and the first sloped, reflective surface 262, anyBY magnetic field components have a minimal effect on the polarizedlight 252 traveling along the y-axis. For convenience, the term “opticalsensor” or “sensor” refers to the structures of the optical sensorassembly through which the light passes, such as the prism 244 and theinput and output elements 248, 250. The term “optical sensor assembly”can include additional components or elements. The term “optical sensor”includes or encompasses the term “electro-optical sensor,” which isinterchangeable with the term “optical sensor.”

In FIG. 18, the optical sensor assembly 240 has been rotated 90 degreesaround the x-axis such that the prism 244 is disposed in the airgap 60so that the incoming light beam 202 enters the prism 244 in a z-axisdirection that is substantially parallel to the z-axis direction of theelectrical current in the current carrying cable 12. Here, the z-axisdepth of the housing 30 is dimensioned to accommodate the bending radius(shown as radius R in FIG. 23A) of the optical fibers 266, and 268A,B asthey are bent to travel along the y-axis direction to the light analyzer50 in implementations where it is positioned below the optical sensorassembly 240. Because the polarized light 252 enters the high Verdetconstant material of the prism 244 long the z-axis direction, which isorthogonal to both the x- and y-components of unwanted magnetic fieldsinduced by the current in the current carrying cable 12 or an adjacentcable 212, the polarized light 252 will be all but unaffected by the BYcomponent of unwanted magnetic fields. This implementation will bedescribed in more detail below.

FIG. 19 is a perspective view of an optical sensor assembly 240 in whichthe optical fibers 266, 268A, 268B extend downwards (relative to earth)along the y-axis away from the current carrying cable 12. FIG. 20 is thesame view with the surfaces shaded to show some of the internalstructures and light paths within the optical sensor assembly 240. FIGS.21A-21D are top, first end, side, and second end views, respectively, ofthe optical sensor assembly 240 shown in FIGS. 19 and 20. The discussionthat follows for this exemplary implementation will make reference toFIGS. 19, 20, and 21A-21D.

The prism 244 includes a pair of prism caps 261 arranged at a 45 degreeangle to cover the total internal reflection (TIR) surfaces orreflective surfaces 262 that change the direction of the polarized lightby 90 degrees each time it strikes the corresponding TIR or reflectivesurface 262 to cause double reflection of the polarized light. The prism244 (including the prism caps 261) has an overall length, designated asLSENSOR in FIG. 21A. The input light polarizing element 248 is apolarizing beamsplitter (PBS) in this example, which is mounted directlyto a bottom surface 259 of the prism 244. The term “bottom” herein isnot intended to reflect any particular orientation of the surfacerelative to earth, but rather to distinguish the various surfaces of theoptical sensor assembly with different terms. In this example, however,due to the orientation of the optical sensor assembly 240, it isconvenient to refer to the surface 259 as a bottom surface becauserelative to earth, this bottom surface 259 is at the bottom of the prism244. However, as will be discussed with reference to the orientationshown in FIG. 18 or 24, the “bottom” surface 259 is not necessarily at abottom orientation relative to earth. The input PBS 248 is mounted tothe prism 244 in such a way as to not extend the overall length,LSENSOR, of the sensor 240. Thus, an end surface 283 (FIG. 21D) of theinput PBS 248 is flush with an end surface 281 (FIG. 21D) of the prism244, or at least the end surface 283 of the input PBS 248 does notextend beyond the end surface 281 so that the overall length of thesensor 240 is constrained by LSENSOR.

Likewise, the output polarizing element 250 in this example is apolarizing beamsplitter

(PBS), which is also mounted to a transmitted light surface 257 (FIG.20) of the prism 244. The transmitted light surface 257 corresponds tothe bottom surface 259, but the transmitted light surface 257 is an areaof the bottom surface 259 out of which the rotated, polarized lightexits the prism 244 and enters an outer incident light surface 255(FIGS. 19, 20) of the output PBS 250 that opposes the outer transmittedlight surface 257 of the prism 244. The output PBS 250 includes achamfered surface 253 (FIG. 19) that is flush with an end surface 271(FIG. 19) of the prism 244, or at least the chamfered surface 253 of theoutput PBS 250 does not extend beyond the end surface 271 of the prism244 so that the overall length of the sensor 240 is constrained byLSENSOR. In these examples, therefore, no part of the output PBS 250 andno part of the input PBS 248 extend beyond a longest dimension of theprism 244, LSENSOR. The chamfered surface 253 is cut so as not tointerfere with the beam splitting interfaces 249A,B (seen in FIG. 20)inside the output PBS 250. Alternately, the beam splitting interfaces249A,B can be positioned within the output PBS 250 so that a sufficientamount of glass can be cut away to form the chamfered surface 253 sothat it can be flush with the end surface 271.

To keep the overall length of the sensor 240 as short as possible, theoutput PBS 250 is rotated at a 45 degree angle from an end edge 271 ofthe prism 244 and extending along a length of the prism 244 (FIG. 21A).The length, LSENSOR, is at least as long as the desired optical pathlength L (FIG. 20) across the airgap 60. According to the Faradayeffect, the rotation angle of the polarized light is a function of theVerdet constant of the material (typically glass), the magnetic fluxdensity, and the optical path length, L. The rotation of the output PBS250 relative to the prism 244 is done in such a manner so as not toincrease the overall length of the sensor 240.

The output PBS 250 is a rhomboid PBS that splits the rotated, polarizedlight 252C into two light beams, with approximately half of the opticalintensity being received by the first optical collimator 267A and theother half of the optical intensity being received by the second opticalcollimator 267B (FIG. 19). Accordingly, the output PBS 250 has a length,LOUTPUT PBS that is twice a length of the input PBS 248, LINPUT PBS(FIG. 19). A width of the input PBS 248, WINPUT PBS, is not greater thanor is equal to a corresponding width of the prism, WPRISM (FIG. 21D). Awidth of the output PBS 250, WOUTPUT PBS (FIG. 21A), is not greater thanor is equal to a corresponding width of the prism, WPRISM (FIG. 21D).The overall length of the optical sensor assembly 240, LSENSOR (FIG.21A), does not exceed a length of the prism 244.

FIG. 22 is a perspective view of a more compact (in overall volume)optical sensor assembly 240, in which a half-wave plate 290 issandwiched between the prism 244 and the output PBS 250, and the outputPBS 250 is aligned lengthwise with a length of the prism 244. In thisexample, the half-wave plate 290 is configured to rotate the lightreflected off the reflective surface 271 by 45 degrees before presentingit to the output PBS 250, which splits the optical energy approximatelyin half, one going to each optical collimator 267A,B. Now, the width ofthe output PBS 250 is not greater than the width of the prism 244 andthe half-wave plate 290 such that the overall width, WSENSOR, of thesensor 240 when fully assembled is not increased by the output PBS 250or the half-wave plate 290.

As discussed above, any of the optical sensor assemblies disclosedherein can be oriented along the z-axis direction such as shown in FIG.18. In this example using the optical sensor assembly shown in FIG. 22,the optical fibers 266, 268A,B extend away along the z-axis direction.When the light analyzer 50 is positioned below the sensor assembly 240along the y-axis, the optical fibers 266, 268A,B are bent as much astheir bending radius allows. While the disclosure contemplates thisorientation, in another implementation, the sensor 240 can still beinserted into the airgap 60 along the z-axis direction, while theoptical fibers (and optional collimators 265, 267A,B) extend along they-axis direction.

Referring to FIGS. 23A-23C, a 45-degree prism mirror 291 is mounted tothe input PBS 248, and a 45-degree prism mirror 292 is mounted to theoutput PBS 250. The optical sensor assembly 240 shown in FIGS. 23A-23Cis the same as the optical sensor assembly 240 shown in FIG. 22, exceptthat the prism mirror 291 is mounted to the bottom surface of the inputPBS 248, which changes the direction of the incoming light beam 202entering the input PBS 248 along the y-axis by 90 degrees from they-axis to the z-axis, and the prism mirror 292 is mounted to the bottomsurface of the output PBS 250, which changes the direction of therotated, polarized light 250A,B exiting the output PBS 250 by 90 degreesfrom the z-axis direction to the y-axis direction, which is shown inFIG. 24 with the sensor assembly 240 installed within the airgap 60.

FIG. 25 depicts an embodiment of a sensor assembly 300 having aplurality of arms 312 a, 312 b that may extend from the base unit 350.The arms 312 a, 312 b may be any type of suitable arms that allow thesensor assembly 300 to connect to one or more electrical cables. In atleast one embodiment, the arms 312 a, 312 b are anti-rotational arms.The use of extension arms 312 a, 312 b may facilitate the ability tohang the sensor assembly 300 onto a primary voltage cable 310 whileenabling a secondary electrical cable 314 to run through a sensor corecurrent concentrator 313. This may occur by displacing the core currentconcentrator 313 from the primary electrical cable 310. The sensorassembly 300 may include any of the components or features discussed inthe embodiments depicted in FIGS. 1-24.

The extension arms 312 a, 312 b of the sensor assembly 300 may bespecially designed, anti-rotational arms, which have been engineered toprevent rotation and twisting. The anti-rotational feature of theextension arms 312 a, 312 b may prevent rotation and twisting of thesensor assembly 300 due to geological or climate phenomena such as earthmovements, wind or other weather-related events.

The sensor assembly 300 may be clamped to a primary electrical cable 310by one or more clamping devices 311, each of which may be attached to anextension arm 312. The extension arms 312 may connect the clampingdevices 311 to base unit 350 of the sensor assembly 300 allowing thesensor assembly 300 to be connected to the primary electrical cable 310.

The base unit 350 may include a core concentrator 313, a flange plate316 and an insulated sensor body 317. The core concentrator 313 mayserve as a current sensor. In at least one embodiment embodiment, asecondary electrical cable 14 passes through the core concentrator 313,and is held in place by alignment loops 315. The alignment loops 315 maybe attached to the extension arms 312. The secondary electrical cable314 may be an electrical cable tapped off of the primary electricalcable 310, allowing a portion of current to be redirected to a secondarycircuit. Passage of the secondary electrical cable 314 through the coreconcentrator 313 may enable measurement of the current running throughthe secondary electrical cable 314. The alignment loops 315 may helpensure that the secondary electrical cable 314 is optimally alignedwithin the core concentrator 313, as movement of the cable within theconcentrator 313 may result in erroneous current readings. In at leastone embodiment, the alignment loops 315 align the secondary electricalcable 314 in the center of the core concentrator 313.

The extension arms 312 may connect to an insulated sensor body 317 byany suitable means. In at least one embodiment, the extension arms 312are attached to flange plates 316 extending from a top end of theinsulated sensor body 317. One or both extension arms 312 may serve aspick-off rods, which are electrodes in contact with, and at the samevoltage potential as, the primary electrical cable 310. Thus, theextension arms 312 may generate an electric field across a voltagesensor 345 embedded within the insulated sensor body 317 to allow thevoltage of the primary electrical cable 310 to be measured. In thepresent invention, voltage may be measured optically by way of thePockels effect as described in U.S. patent application Ser. No.15/679,624. The insulated sensor body 317 may be made from any suitablematerial, such as a non-conductive material. In at least one embodiment,the insulated sensor body 317 is made from a cycloaliphatic epoxy. Aground connection 318, for connection of a ground cable, and aconnection 319, may be located at the bottom end of the insulated sensorbody 317. In at least one embodiment, the ground connection 318 is a nutconfigured to attach to a ground cable. In at least one embodiment, theconnection 319 may be a connection to an optical cable, such as a strainrelief boot. The flange plates 316 may be made of any suitableconductive or non-conductive material.

The extension arms 312 a, 312 b, may be made from any suitable material.In at least one embodiment, extension arm 312 a is made from aconductive material, whereas extension arm 312 b may be made from eithera conductive or non-conductive material. The flange plate 316 may alsobe made from any suitable material. In at least one embodiment, theflange plate is made from a conductive material. The conductive materialmay include copper, aluminum, silver, or other materials that permiteasy flow of electrons under a voltage potential. The non-conductivematerial may include cycloaliphatic epoxies, rubber, plastics, and anymaterials that block the flow of electrons under a voltage potential.

FIG. 26 further depicts the components of the sensor assembly 300. Theclamping devices 311 may be top mounting clamps and may includeanti-rotational holders that connect and secure the sensor assembly 300to a primary electrical cable 310. The clamping devices 311 may be madefrom any suitable material. In at least one embodiment, the clampingdevices 311 may be made from a conductive material. For example, theclamping devices 311 may be made from conductive materials that includecopper, aluminum, silver, or other materials that permit easy flow ofelectrons under a voltage potential. The clamping devices 311 may useany suitable means to attach to an electrical cable. For example, theclamping devices 311 may include an eye bolt 320, which may tighten themounting clamp onto an electrical cable. The clamping devices 311 mayalso attach to a top end of the extension arms 312 a and 312 b in anysuitable manner. For example, the clamping devices 311 may include abolt, screw or similar structural feature that permits it to attach tothe extension arms 312 a, 312 b.

The bottom end of the extension arms 312 a and 312 b may attach to theflange plate 316. The extension arms 312 a, 312 b may include one ormore alignment loops 315. The alignment loops 315 may be located at anysuitable position on the extension arms 312 a, 312 b, such that they areconfigured to support a secondary electrical cable 314. The alignmentloops 315 may be made from any suitable material. In at least oneembodiment, the alignment loops 315 are made from an insulatingmaterial. The alignment loops 315 may be configured to position asecondary electrical cable 314 such that the secondary electrical cable314 is aligned within the core concentrator 313.

The connections between the clamping devices 311 and extension arms 312are depicted in FIG. 27. As shown in Detail A of FIG. 27, one end of theclamping devices 311 may include a ridge 321 and a projection 322 thatengages with a top end of the extension arms 312. The projection 322 maybe any suitable type of projection, such as a rod, bolt, etc. The topend of the extension arms 212 may include an opening 323 configured toengage with the projection 322. In at least one embodiment, the opening323 is configured to lockingly engage the projection 322. For example,the opening 323 may include threads to engage corresponding threads onthe projection 322. The ridge 321 on the clamping device 311 may beconfigured to engage with a groove 324 in top of the extension arms 212.The connection between the ridge 321 and groove 324 may prevent twistingor rotation between the clamping device 311 and the extension arm 212.

As shown in Detail B in FIG. 27, one end of the extension arm 312,opposite the end configured to attach to the clamping device 311, mayinclude a ridge 327. The ridge 327 may be configured to engage with anopening 325 in the flange plate 316. The flange plate 316 may alsoinclude a projection 326 that extends outwardly from the flange plate316. The projection 326 may be configured to engage with a correspondingopening (not shown) on the end of the extension arm 312. In at least oneembodiment, the extension arms 312 is configured to lockingly engagewith the flange plate 316. For example, the projection 326 may includethreads that engage with corresponding threads in the opening on the endof the extension arm 312. The attachment between the ridge 327 andopening 325 in the flange plate 316 may prevent twisting or rotationbetween the extension arm 312 and the flange plate 316. As shown inFIGS. 27 and 28, at least one embodiment, the flange plate 316 mayinclude one or more apertures 333. The apertures 333 may facilitatehanging or installation of the sensor body onto utility lines. Thiscould be accomplished using a hot stick or similar non-conductive pole.

As shown in FIG. 29, the ground connection 318 and connection 319 can beseen with respect to the sensor assembly 300. The ground connection 318and connection 319 may be attached to or part of the insulated sensorbody 317. In at least one embodiment, the clamping devices 311 mayinclude a tightening mechanism 320 to tighten the clamping device 311 toan electrical cable.

Each of the optical sensors shown in FIGS. 16-29 has a very high dynamicrange for sensing a wide range of current magnitudes. At the same time,the sensors are highly sensitive to a magnetic field of interest in adirection parallel to the linear polarized light traversing the airgap,but highly insensitive to unwanted or stray magnetic fields induced bynearby current carrying cables, such as carrying other phases ofcurrent. The resulting optical sensor is highly accurate, very compactin size, and can be oriented within an airgap in any orientationregardless of which axis along which the airgap lies. This flexibilityallows for more degrees of freedom in designing housings for the sensorswithout sacrificing accuracy, sensitivity, or size. The small size ofthe optical sensor allows it to be placed closer to the magneticconcentrator, resulting in stronger magnetic fields that produce largerangles of rotation. As a result, smaller magnitudes of current can bedetected by the optical sensor.

Thus, numerous variations exist of combination and location of lightsource, polarizers and beamsplitter relative to the light directingdevice. All are within the scope of the implementations and aspectsdisclosed herein.

Those skilled in the art will recognize that light directing devices mayprovide more than one output per device, as to the same or differentcharacteristics. Many devices, amplifiers, filters, analog to digitalconverters and others may be multi-channeled and capable of handlingmore than one channel of information may be used, with differentscaling, to enable different instruments to be operably connected to thesystem, or a single instrument may be connected with multiple inputs.

While illustrative examples are provided, those skilled in the art maydevise alternative arrangements and components to meet the specific needfor reflection. Such alternative embodiments and equivalents should beconsidered within the scope of the present disclosure. Equivalentmethods such as the use of reflective surfaces or thin film refractivesurfaces should be considered within the scope of the presentdisclosure.

The word “prism” is used to describe the light directing device, in someembodiments. From an inspection of FIG. 7, and FIGS. 10-24, it may beseen that the term is intended to include a variety of shapes. Thesimplest shape is an isosceles trapezoid, having a top and bottomparallel surfaces, the top surface sloping downwardly at both ends tothe bottom parallel surface. See, for example, FIG. 13. FIGS. 10 and 12illustrate a prism having the shape of an irregular hexagon, having topand bottom parallel surfaces, four parallel sides and two inwardlysloping upwards sides at the top. FIG. 11 is an even more irregularshape, having only one upwardly sloping side. FIGS. 14 and 15 illustratethat the light directing device may be linear in shape. All of suchshapes are included within the meaning of the word “prism” herein.

As used in this application, the words “a,” “an,” and “one” are definedto include one or more of the referenced item unless specifically statedotherwise. Also, the terms “have,” “include,” “contain,” and similarterms are defined to mean “comprising” unless specifically statedotherwise. Furthermore, the terminology used in the specificationprovided above is hereby defined to include similar and/or equivalentterms, and/or alternative embodiments that would be considered obviousto one skilled in the art given the teachings of the present patentapplication.

What is claimed is:
 1. An optical sensor assembly for measuringelectrical current in a current carrying cable, comprising: a sensorbody having a first end and a second end; a concentrator core formeasuring current, the concentrator core attached to the first end ofthe sensor body; a plurality of extension arms extending from the firstend of the sensor body; a plurality of clamping devices, each of theplurality of clamping devices configured to attach to a top end of oneof the plurality of extension arms; and at least one alignment loopattached to each of the plurality of extension arms; wherein theclamping devices are configured to engage with a first electrical cable;wherein the at least one alignment loop is configured to engage with asecond electrical cable, and wherein the core concentrator at leastpartially surrounds the second electrical cable and measures theelectrical current in the second electrical cable.
 2. The optical sensorassembly of claim 1, further comprising: a plurality of flange plates,wherein each of the plurality of flange plates is connected to the firstend of the sensor body and a bottom end of one of the plurality ofextension arms.
 3. The optical sensor assembly of claim 1, wherein atleast one of the plurality of extension arms is made from anon-conductive material.
 4. The optical sensor assembly of claim 1,wherein at least one of the plurality of extension arms is made from aconductive material.
 5. The optical sensor assembly of claim 1, whereina first one of the plurality of extension arms is made from a conductivematerial and a second one of the plurality of extension arms is madefrom a non-conductive material.
 6. The optical sensor assembly of claim1, wherein the core concentrator is configured to pivotally move betweenan open and closed position and at least partially surrounds the secondelectrical cable when in the closed position.
 7. The optical sensorassembly of claim 1, wherein the core concentrator has an airgap suchthat when the core concentrator at least partially surrounds the secondelectrical cable a magnetic field in the airgap is induced, which isindicative of the current in the second electrical cable.
 8. The opticalsensor assembly of claim 1, wherein a voltage sensor positioned in thesensor body is configured to measure voltage of the first electricalcable when the plurality of clamping devices are connected to the firstelectrical cable.
 9. The optical sensor assembly of claim 1, whereineach of the plurality of clamping devices are removable from theplurality of extension arms.
 10. The optical sensor assembly of claim 1,wherein the at least one alignment loop position the second electricalcable in the center of the core concentrator.
 11. The optical sensorassembly of claim 2, wherein each the plurality of extension arms areremovably attached to at least one of the plurality of flange plates.12. An optical sensor assembly for measuring electrical current in acurrent carrying cable, comprising: a sensor body having a first end anda second end; a voltage sensor positioned within the sensor body; aconcentrator core for measuring current, the concentrator core attachedto the first end of the sensor body; a plurality of extension armsextending from the first end of the sensor body; a plurality of clampingdevices, each of the plurality of clamping devices configured to attachto a top end of one of the plurality of extension arms; and at least onealignment loop attached to each of the plurality of extension arms,wherein the clamping devices are configured to engage with a firstelectrical cable, wherein the at least one alignment loop is configuredto engage with a second electrical cable, wherein the core concentratoris configured to pivotally move between an open and closed position andat least partially surrounds the second electrical cable when in theclosed position, and wherein the voltage sensor is configured to measurethe voltage in the first electrical cable when the clamping devices areengaged with the first electrical cable.
 13. The optical sensor assemblyof claim 12, further comprising: a plurality of flange plates, whereineach of the plurality of flange plates is connected to the first end ofthe sensor body and a bottom end of one of the plurality of extensionarms.
 14. The optical sensor assembly of claim 12, wherein at least oneof the plurality of extension arms is made from a non-conductivematerial.
 15. The optical sensor assembly of claim 12, wherein at leastone of the plurality of extension arms is made from a conductivematerial.
 16. The optical sensor assembly of claim 12, wherein a firstone of the plurality of extension arms is made from a conductivematerial and a second one of the plurality of extension arms is madefrom a non-conductive material.
 17. The optical sensor assembly of claim13, wherein each the plurality of extension arms are removably attachedto at least one of the plurality of flange plates
 18. The optical sensorassembly of claim 13, wherein the top end of each of the plurality ofextension arms includes a groove configured to engage with a ridge on abottom end of one of the plurality of clamping devices.
 19. The opticalsensor assembly of claim 18, wherein the top end of each plurality ofextension arms includes an aperture configured to engage with aprojection on the top of one of the plurality of clamping devices. 20.The optical sensor assembly of claim 19, wherein each of the pluralityof clamping devices is lockingly engaged with one of the plurality ofextension arms.